Onboard LAN/video/audio

[cdrakejr]

Do the onboard LAN/video/audio capabilities of a motherboard use IRQ's or do they actually leave IRQ's free?
Thanks!

 

[chemwiz]

They use IRQ's, just like a card would. It's just cheaper to use the onboard stuff, you can find motherboards with nic/sound/modem/video built in for $70.

 

[MonkeyK]

Do they use more CPU than a card would?

 

[chemwiz]

No, but sometimes the video doesn't have it's own memory, it shares the system memory, so you lose some RAM and speed with those.

 

[gaidin123]

One advantage to onboard peripherals like NICs, sound, etc. is that they only use some bandwidth between the north and south bridge chips and do not take up any of the 133MB/sec of the PCI bus. So if you really needed to saturate the slow PCI bus it would be to your advantage to use integrated features of many modern motherboards.

But yeah they still use IRQs and if a built in feature breaks, you gotta buy a whole new motherboard.

Gaidin

 

[Athlon4all]

Originally posted by: gaidin123
One advantage to onboard peripherals like NICs, sound, etc. is that they only use some bandwidth between the north and south bridge chips and do not take up any of the 133MB/sec of the PCI bus. So if you really needed to saturate the slow PCI bus it would be to your advantage to use integrated features of many modern motherboards.

I don't think that is the case to be honest. Maybe someone else can clairfy, but Im pretty certain that even on-chip (ie on the die of the south bridge) devices typically are just connected to the PCI bus like a card would, and certainly external solutions (ie all the realtek on-board LAN's, all the CMedia Audio, all the NEC USB2 Chip boards, etc) are connected to the PCI bus. Sure there are some onboard stuff that aren't on the PCI bus but most are still just devices on the PCI bus.

 

[gaidin123]

When I responded originally I was thinking of Peter's post in Subscriber Forums this thread. Now once Peter stumbles on this thread I don't want him to think I took his word as gospel but it seems to make sense to me.

I agree that the off chip integrated peripherals like sound, lan, etc. will probably take up PCI bandwidth, but I believe that integrated stuff that's on one of the bridge chips doesn't use PCI bandwidth. Though if anyone can point me to a FAQ or something that'd be most appreciated.

Gaidin

Edit: For older motherboards that used the PCI bus as the link between the North and South bridge chips of course the PCI bus bandwidth will be taken up from integrated stuff. But now with Via's V-Link, or AMD's Hypertransport, and other bus links between the 2 chips integrated stuff (on those 2 chips) won't use PCI bandwidth. (from the 2nd page of Tom's Hardware's nForce2 article)

 

[Peter]

In the modern chipsets (that do not connect the south bridge through PCI anymore), the _integrated_ functions (IDE, USB, sound, LAN, whatever else) indeed do not eat into PCI bandwidth anymore.

_Onboard_ (mind the difference) extra functions like RAID controllers of course connect to the PCI bus - where else should they be?

regards, Peter